1. Field of the Invention
This invention relates to a method for stabilizing a taste-modifier which comprises fresh Curculigo latifolia fruits, dried fruits thereof or a curuculin-containing material obtained therefrom.
2. Description of the Prior Art
Known taste-modifiers which affect the receptor membranes on the tongue in such a manner as to modify the taste of a food, include those which remove the sweetness of a sweet food in the mouth, for example, gymnemic acid contained in Gymnema sylvestre leaves and ziziphine contained in Ziziphus jujuba leaves; and those which convert the sourness of a sour food into sweetness in the mouth, for example, miraculin contained in Synsepulm dulcificum fruits.
Although miraculin has the abovementioned effect, it is not put into practical use as a taste-modifier because of its poor stability.
The present inventors have found that a sour material or water taken after eating Curculigo latifolia fruits would taste sweet. Thus they have attempted to identify the sweetness-inducer. As a result, they have found that a specific protein contained in Curculigo latifolia fruits is the aimed sweetness-inducer (cf. Japanese Patent Application No. 153143/1988). This protein is named curuculin. In order to utilize this curculin as a taste-modifier on a commercial scale, it is required to obtain crude curculin in a stable form from Curculigo latifolia fruits as efficiently as possible.
Pure curuculin may be obtained by washing fresh Curculigo latifolia fruits or dried fruits thereof with water, extracting from them with an aqueous solution of a salt and purifying the extract by ion-exchange chromatography with the use of CM-Sepharose and HPLC with the use of a gel column. Pure or almost pure curculin would remain stable for a month or longer in the form of an aqueous solution at room temperature. However fresh Curculigo latifolia fruits, dried fruits thereof or crude curuculin, in particular, in the form of an aqueous solution, would have a poor stability upon storage since they are contaminated with proteases and bacteria contained in the Curculigo latifolia fruits.